Understanding the Snow Drought–Soil Moisture–Vegetation Feedback: The impacts of seasonal Memory Effects on GPP Anomalies

Snow plays a critical role in ecosystems by providing a reliable water supply in spring as winter snow melts. However, “snow droughts” are emerging as a growing threat to terrestrial ecosystem functioning. Snow droughts, characterized by reduced or even absent winter snow accumulation, arise either from warmer conditions where precipitation falls as rain instead of snow (warm snow drought) or insufficient winter precipitation (dry snow drought). Consequently, the amount of water stored in the snow pack (“snow water equivalent”, -(SWE)) is reduced, altering snow melt and thus impacting streamflow discharge and groundwater recharge. Even more directly, soil water storage is reduced, which can diminish late-season water availability, potentially reducing plant productivity. Despite their critical implications, the links between snow droughts and their broader effects on the carbon cycle remain poorly understood and quantified.

 Using the LPJmL dynamic global vegetation model, we attribute spring gross primary productivity (GPP) anomalies in the Northern Hemisphere over the past decades to snow drought-induced soil moisture deficits. By tracking the seasonal progression of soil moisture and GPP, we quantify these linkages between snow droughts and subsequent soil moisture deficits, as well as their direct impact of GPP anomalies and their related “legacy or memory effects” on summer GPP anomalies.

This research highlights the feedback mechanisms between snow droughts, soil moisture, and vegetation, providing novel insights on drought impacts across seasons.